This relates generally to imaging systems, and more particularly to imaging systems with bond pad structures.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imaging systems (i.e., image sensors) often include a two-dimensional array of image sensing pixels. Each pixel typically includes a photosensitive element such as a photodiode that receives incident photons (light) and converts the photons into electrical signals. The imaging system contains an image sensor die with an image sensor integrated circuit and an array of photodiodes.
Circuitry within the image sensor die is typically coupled to a bond pad that interfaces with external components. A first passivation layer is formed over the bond pad to passivate the bond pad. This passivation layer is then opened to allow wirebonding. After the passivation layer is formed, an array of color filter elements is formed on the image sensor die. An array of microlenses is then formed over the array of color filter elements. The color filter and microlenses are formed on the wafer surface through a spin-on process. Due to the topography of the bond pad and the passivation layers the spin-on process creates streaks and other artifacts on the wafer. This results in lower yield. Therefore, this process of forming image sensor dies is inefficient and costly and often results in image sensors that suffer from planarity issues.
It would therefore be desirable to provide improved ways of manufacturing image sensor dies.